Process of producing cellulose acetate yarn



Patented June 6, 1933 PATENT OFFICE CAMILLE DREYFUS, OF NEW YORK, N. Y., AND WILLIAM IVHITEHEAD, OF CUMBERLAND, IY'IABYLAND, ASSIGNORS TO CELANESE CORPORATION OF AMERICA, OF NEW YORK,

N. Y., A CORPORATION OF DELAW'ARE PROCESS OF PRODUCING CELLULOSE ACETATE YARN No Drawing.

This invention relates to the preparation of yarns or films containing cellulose acetate from solutions containing the same.

An object of our invention is to prepare yarn from a cellulose acetate, which yarn does not deluster when exposed to boiling water or other delustering agencies that are apt to cause delustering of previously known cellulose acetate yarns.

A further object of our invention is to prepare yarn from cellulose acetate, which yarn is of greater strength, as shown by its tenacity properties, than previously known cellulose acetate yarns.

A further object of our invention is to use a solvent of very high concentration for preparing the solution of cellulose acetate used in spinning the yarn. Other ob ects of our invention will appear from the following detailed description.

Yarns or fabrics produced from acetone soluble cellulose acetate or other cellulose acetates, when prepared in accordance with prior processes, lose their luster and become opaque, when treated with very hpt or bolling water. This delustering action is accentuated by the presence of soaps or certain salts. Therefore in the washing of such yarns or fabrics, care must be taken that the temperature of the washing bath be not too high, else delustering may result.

As an example of the prior methods of preparing yarns from acetone soluble cellulose acetate, it may be pointed out that such a cellulose acetate having an acetyl value of, for instance, 54.5% and containing a normally moisture content of 5% was dissolved in a solvent containing 95% of acetone and 5% of water. The solution thus formed was spun through the orifices of a spinneret, either into an atmosphere of elevated temperature, whereupon the solvent is evaporated, as in the case of dry spinning, or into a precipitating loath as in the case of wet spinning. Yarns produced in accordance with this method display the undesirable property of becoming delustered or crinkle-d when exposed to water or wet steam at elevated temperature. Apparently the delustering of the yarn may be due to the fact Application filed February 4, 1928. Serial No. 252,031.

that it becomes crinkled and the surface thereof becomes pitted, or may be due to any other reason.

lVe have discovered the surprising fact that if a substantially bone dry cellulose -acetate, as set forth above, is spun from a solution containing practically the pure acetone with substantially no diluent present, the strength of the resulting yarn is increased to a large extent and the tendency of the yarn to deluster when exposed to boiling water is decreased enormously. e have found that the purer the solvent used, the greater are the strength and resistance to delustering of the yarns.

In accordance with our 'inventiomyarns or films are made from a cellulose acetate which forms yarns or films that tend to deluster when spun in the old manner. The cellulose acetate, which contains about 5% of water, is thoroughly dried and is then dissolved in a solvent containing very little, if any, diluent, and is then spun. The cellulose acetate used in our invention may or may not be soluble in acetone, but we prefer to use an acetone soluble cellulose acetate having an acetyl value of 52.5% to 56% and preferably 54.5%, but this invention is not limited to the use of such cellulose acetate.

As stated before, the cellulose acetate used should be bone dry or as nearly freefrom water as possible. In order to obtain this result, the ordinary cellulose acetate containing about 5% of water, is dried under vacuum until it contains less than 1% of moisture. It is then cooled under vacuum and without permitting it to become exposed to the atmosphere, it is submerged in, or otherwise treated with the solvent. lVhile we do not limit ourselves to the specific solvent used in our process, we have found that the use of acetone as the solvent gives excellent results. If a small proportion of diluent is used, it may be water or any other suit-able diluent or liquid. However, this invention will be more specifically described with reference to the use of water as a diluent, when a diluent is used.

The amount of water present in the acetone should be very small and may vary from practically no water (say 0.06%) as found in chemically pure acetone, to about 2.5% of water as found in a 97.5% acetone solution. We have found that by the use of chemically pure acetone containing but only 0.06% of water, a yarn having maximum tenacity and elongation factors and a good resistance to delustering may be produced. A yarn made from a solvent containing 99% of acetone and 1% of water, while showing greater tenacity, elongation and resistance to delustering than an ordinary yarn made from say, 95% acetone is not as strong and deluster resistant as that n ade from acetone of higher concentration.

We have also found that yarns of increased strength are obtained by using solvent mixtures containing appreciable amounts of say 16%, 22% or 28% diluent, say solvent mixture containing (1) 78% of acetone and 22% of water, (2) 76% of acetone and 24% of water, or (3) 72% of acetone and 28% of water.

As stated before, the solution may be spun by the wet or.by the dry spinning method. However, we prefer to employ a dry spinning method. In dry spinning, the temperature of spinning is of importance for obtaining the best results. We have found that for the solvent used in this invention, a temperature of to C. may be used, but we do not limit ourselves to this temperature.

Yarns produced by the above described method, when boiled in water or water containing soap or other alkaline material, or when exposed to wet steam, show a greatly increased resistance to delustering as compared with yarns produced from a solution containing say, 95% acetone and 5% water. Moreover, the tenacity and elongation of such yarns are greater than those of yarns prepared from a solution containing say 95% of acetone and 5% of water. Thus, with a given cellulose acetate, yarns produced in ac cordance with our invention, are of 15% to 20% or more greater dry strength and of 20% to 25% or more greater wet strength than are yarns spun from a solvent mixture containing say, 95% of acetone and 5% of water.

In order to further illustrate our invention but without intending to be limited thereto, the following detailed description of an example will be given.

Example e takea cellulose acetate having an acetyl value of 54.5%, a moisture content of 5% and a viscosity of 20 (as determined on an Ostwald viscosimeter with a solution containing 6 grams of cellulose acetate and 100 grams of acetone, the viscosity of glycerine being called 100). This cellulose acetate is placed in a vacuum dryer where it is dried at elevated temperature under a vacuum of 25 inches of mercury (i. e. 5 inches of mercury absolute pressure), until its moisture content is reduced below 1%. The cellulose acetate is dried under vacuum and then withdrawn and sealed against the air, or else immediately immersed in acetone containing but 0.06% of water. The amount of acetone used is that required to form a solution containing approximately 25% of cellulose acetate. The solution is then filtered and spun in a dry spinning machine, in which the solvent is evaporated off at a temperature of 50 to 55 C. and the thread thus formed is gathered up and wound or reeled. The yarn produced in this manner shows a remarkable resistance to delustering. Thus while a yarn produced from a solution containing 95% of acetone and 5% of water becomes almost completely delustered or crinkled, when boiled in water for a period of 15 minutes, the yarn made in accordance with this example, when boiled for 15 minutes, has its luster practical.- ly uneifected and is but slightly delustercd after minutes boiling. Even boiling in an 0.5% soap solution hardly effects the luster of the yarn prepared in accordance with this example. Moreover, the strength of the yarn produced in accordance with this example is much greater than that of yarns prepared from the same cellulose acetate from a solvent mixture containing 95% of acetone and 5% of water as shown by the tests of yarns of 150 denier containing 26 filaments, given in the following table.

Yarn prepared from Yum prepared from solvent mixture acetone containing containim 95% 006% H2O tone and 5% water Tenacity, dry 1.42 g. per denier 1.26 yr. per denier Tenacity, wet 0.87 g. per denier 0.79 g. per denier Elongation, dry 29.2% 26.0% Elongation, wet 42.5% 33.0%

The tenacity and elongation were measured in the usual manner in a serimeter at 735 F. with a relative humidity of the air of 64%.

The process of this invention may be applied to the obtaining of many beautiful effects in woven and knitted fabrics. For instance, a fabric may be woven of which the warp consists of yarn spun from a charge dissolved in substantial chemically pure acetone while the weft may consist of a yarn spun from a charge dissolved in a solvent mixture containing 95% of acetone and 5% lustrous on one side and which has a dull matte appearance on the other.

By way of further illustration it is pointed out that lustrous figures or designs against dull background or vice versa may be obtained by weaving the two kinds of yarn by well known mechanical expedients of weaving and by subsequently boiling or steaming.

While this invention has been described specifically with respect to the use of cellulose acetate, it may also be applied to such cellulose esters, such as cellulose tormate, cellulose acetate, or cellulose propiona-te, that display the same properties as the cellulose acetate described above.

It is to be understood that the expression solvents of certain concentrations as used in the appended claims includes solvents or solvent mixtures of certain concentration or degree of admixture.

It is to be understood that the foregoing details are given merely by way of illustration and that many variations may be made therein without departing from the spirit of this invention.

Having described our invention what we claim and desire to secure by Letters Patent 1s:

1. In the method of producing articles containing organic esters of cellulose, the step of dissolving the organic esters of cellulose, after it has been dried, in a substantially undiluted solvent.

2. Method of producing articles containing cellulose acetate comprising dissolving the cellulose acetate, after it has been dried, in asolvent of a concentration from substantially 97.5% to 100%, and then evaporating the resulting solution.

3. Method of producing yarns containing cellulose acetate comprising dissolving the cellulose acetate, after it has been dried, in a solvent of a concentration from substantially 99% to 100%, and then spinning the re sulting solution.

4. Method of producing yarns. containing cellulose acetate comprising dissolving cellulose acetate, after it has been dried, in acetone of a concentration from 97.5% to 100% and then spinning the resulting solution.

5. Method of producing yarns containing cellulose acetate comprising dissolving cellulose acetate, after it has been dried, in acetone of a concentration from substantially 99% to 100%, and then spinning the resulting solution.

6. Method of producing yarns containing cellulose acetate comprising dissolving cellulose acetate, after it has been dried, in substantially chemically pure acetone and then spinning the resulting solution.

7. Method of producing yarns containing cellulose acetate comprising dissolving cellulose acetate, aiter it has been dried, in substantially chemically pure acetone and then dry spinning the resulting solution, whereby yarns that are resistant to the delustering action of boiling water and are of greater strength are produced.

8. Method of producing yarns that are resistant to the delustering action of boiling water from cellulose acetate that normally forms yarns that are readily delustered by the action of boiling water comprising drying such cellulose acetate, dissolving it in acetone of substantially 99% to 100% concentration and then spinning the same.

9. Method of producing yarns that are resistant to the delustering action of boiling water from cellulose acetate that normally forms yarns that are readily delustered by the action of boiling water comprising drying such cellulose acetate, dissolving it in substantially chemically pure acetone and then spinning the same.

10. Method of producing yarns containing cellulose acetate comprising drying acetone soluble cellulose acetate until it contains less than 1% of water, dissolving the same in acetone of substantially 99% to 100% concentration and dry spinning the same.

11. Method of producing yarns containing cellulose acetate comprising drying acetone soluble cellulose acetate until it contains less than 1% of water, dissolving the same in substantially chemically pure acetone and dry spinning the same.

12. Method of producing cellulose acetate yarns comprising drying an acetone soluble cellulose acetate having an acetyl value of from about 52.5% to about 56% until it contains less than 1% of water, dissolving the same in substantially chemically pure acetone, filtering the resulting solution and dry spinning the same at a temperature of 50 to 55 0., whereby yarns are formed that are highly resistant to the delustering action of boiling water, and which have a strength that is 15% to 25% greater than that of yarn produced from a cellulose acetate solution containing 95% of acetone.

In testimony whereof, we have hereunto subscribed our names.

CAMILLE DREYFUS. WVILLIAM WHITEI-IEAD. 

